This question appears to be off-topic. The users who voted to close gave this specific reason:

"Questions must be relevant to professional system administration. Server Fault is dedicated to professional system and network administrators. End user and enthusiast questions are off-topic (contact your system administrator or hire a professional to help you out). Please see the Help Center for more information." – Jenny D, Sven, John, mdpc

It may still be in queue. You always start by talking to the server admin at the sending server.
–
Jenny DJun 18 '14 at 9:58

3

Your assumption that email server will throw error when rejected an email was partially wrong. The server could silently discard your email, although this is not recommended behavior.
–
masegaloehJun 18 '14 at 10:32

This is a good question, it's just not a good fit for ServerFault. Perhaps Superuser would be a better location for it?
–
Avery PayneJun 18 '14 at 21:32

1 Answer
1

Let me explain. Masegaloeh is correct with regard to assumptions, but there is one other explanation that you have overlooked: email is queued. Just because a message is accepted for delivery, doesn't mean that it has been delivered.

And that's just the beginning. The message may travel directly to your mail server, or it may travel through a long, winding route of mail servers. Each mail server along the way may have different policies about what is and isn't acceptable. Each mail server may actually choose to queue your message, or worse, decide to return it back to you ala "return to sender".

Here's another way to think of it; the movement of email from the sender to you is very much a rough analog of the Postal service, in that the message is moved from point to point over time, until it finally reaches the end-point, which is your Inbox. But if we run with that analogy, there are some other things as well. Your message has to contend with random labor strikes (server down), washed out bridges and tornados (network connectivity issues), bandits (malicious hackers), terrorists (malware writers clogging a queue with worms), traveling salespeople selling snake oil (spam clogging a queue), the occasional despot (a "spook" agency looking at what you sent), private mail stops run by tin-pot tyrants (unfriendly email administrators/poorly-configured mail servers), and just sometimes, the dog eats the mail in transit (disk failure).

The short, easier-to-remember rule of thumb is: until it's delivered, never assume that your finished with your message. This is why we have delivery receipts in email; it ensures that it arrived to its destination.